Wood is a living material in which expanding and contracting movements take place in pace with the surrounding air humidity and temperature. It is therefore of great importance that wood to be used for the manufacturing of furniture, be dried to a humidity content of 8 to 10%.
Especially in connection with the manufacturing of pipe-shaped bodies to be used for furniture, the wood-staves must be given such a physical shape and be assembled in such a manner that the pipe-shaped body as a whole must be able to withstand these environmentally dependant oscillations. Besides, since the pipe-shaped body used as furniture will expose both its external and internal surfaces, it is necessary for the achievment of a pleasant and attractive appearance thereof, to avoid any offset between the staves including gaps, distensions and sprawls.
Besides, a furniture design which is based upon the use of a pipe-shaped body of this kind, will not allow the use of reinforcing straps which are clamped around the wood-stave cylinder. Due to the hygroscopic properties of wood material a possible reinforcement means may be tolerated, which embodies inner, invisible means of the same living wood material and with the same wood structure.
From U.S. Pat. No. 1,070,572 (S. F. Wyckoff) there is known an improved form of interlocking joint especially adapted for use in sectional wooden columns or sectional wooden conduits and the like, where it is desirable to have the meeting edges of comparatively long sections interlocked in as simple and inexpensive a manner as possible.
However, since the known pipe-shaped bodies of wood are to be used as columns or conduits, the thickness of each stave is relatively large compared to the overall diameter of the pipe, the large thickness of the staves also being necessary due to the shape of the interlocking grooves and tongues. If the embodiment illustrated in said U.S. Patent Specification is compared to a cylinder having a diameter of for example 62 cm, the known wood-stave interlocking technique would require a stave thickness of 10 cm, which is five times as much as the present technique advising a pipe wall thickness of approximately 2 cm.
Further, the known technique requires very large tongues and grooves, involving a considerable width of each stave, and a considerable amount of wood to be removed from each side edge of the staves, which means a heavy loss of blank material.
This known manufacturing technique would be very unfavourable in connection with the production of furniture, since it requires an unfavourable utilization of materials and time, which is in contrary to effective furniture production in which a rational utilization of time and raw material is prevalent.
If nevertheless this known technique according to U.S. Pat. No. 1,070,572 should be used in furniture production, the required smaller material thickness and accordingly smaller grooves and tongues would involve that only the highest quality of material could be used, i.e. stave material being substantially free from knots, since the smaller material thickness and consequently smaller taps would make the latter very sensitive to breakage during the mounting of the staves.
Further, the mounting of the individual staves to a complete cylindrical body is, due to the arrangement of the grooves and the tongues at an angle to each other, restricted to the staves or sections being slid relative to each other after placing one section adjacent the end of the other section and with its tongue and groove in register with the groove and tongue respectively of the other section. This sliding of the staves relative to each other for the overall mounting thereof to a finished pipe is time consuming as compared to placing a plurality of staves side by side in a cradle for sidewise mounting thereof. The longitudinal sliding of the staves for the interlocking thereof, as suggested by the known technique, would also give an unfavourable utilization of the effect of any glue coated on the side edges of the staves, and consequently a large, unnecessary expenditure of not only glue, but also time and material.
Also as regards any later cutting of the conduits according to U.S. Pat. No. 1,070,572, this known technique would render a large possibility of uneven assembly between the staves due to the hygroscopic properties of the wood. Besides, the known cylinder or conduit includes a multiple of flat outer surfaces, i.e. an outer polygonal circumference. If said flat outer faces should be ground to an overall round outer surface, the outer tap or tongue would be weakened or even damaged, thereby considerably reducing the value and effectiveness of the tongue and groove interlocking system.
Therefore the conduit according to U.S. Pat. No. 1,070,572 can not provide a cylinder which can be cut in any direction and still have a stable configuration and still expose an excellent quality on any surface, both inwardly and outwardly.
From Australian patent specification No. 101195 there are known wood-stave pipes which are reinforced by a spiral winding of wire, in which the pipe barrel or body composed of a plurality of staves is surrounded by a wire reinforcement in helical formation with an interposed tape or ribbon.
Industrial Canada, Jun. 1934, page 59, "Canadian Wood-Pipe & Tanks" describes a "Canadian" Butt Jount including a double-tongue-and-groove construction having twice the strength of an old-type joint.
In British patent specification No. 25380/1904 there is disclosed the construction of hollow columns of regular or irregular taper, such for instance as is called for in the classic order of architecture, and it consists in providing the staves, whereof these columns are formed, with interlocking tongues and grooves, the said interlocking devices being parallel with the edges of the staves and integral therewith.
In all the publications mentioned above, the wood-stave pipes are used as pipes only or as columns extending their full length, but no hint or indication is found for using such wood-stave pipes for furniture, let alone for using such bodies as combined furnitures and sculptures. Neither do these publications give any instructions for how to manufacture a pipe-shaped body of wood having a substantially annular section in an effective and time-consuming manner for thereby providing a cylinder which can be cut in any direction and still by devoid of gaps, distensions or sprawls, while exposing the same smooth and pleasent appearence both as regards its inner and outer surfaces.
U.S. Pat. No. 3,371,963 (Weller) discloses a procedure for convolutely winding multi-ply paper tubes with flat size and rounded corners, and from these paper tubes having parallel sides with interwining rounded corners, there are cut furniture parts.
U.S. Pat. No. 3,722,953 (Hull) relates to chairs, bed, sofas, tables, bookshelves, and other articles of furniture, which are formed of arcuate and cylindrical members, which might be derived, for example, by cutting cardboard tubes into appropriate shapes.
According to these references products are prepared from forms or moulds including square channels with rounded corners, possibly including cylinders which are moulded from various homogenaous masses, or a mould comprising thin layers on top of each other for procuring a sufficiently strong blank material. However, no hints are given of how wooden staves can be assembled in a manner bringing forth smooth and even surfaces on both sides of the cylinder walls.
From an aestethic point of view these products must often be further treated by means of other materials, especially in the area of the edges, and possibly be given a surface treatment to cover or hide the homogeneous mass.
In fact the present invention is primarily a further development of barrel production, but the present method has deviated from this known cooper handcraft technique by paving new ways, thinking in novel combinations, disregarding experienced furniture craftmen's warnings, and by using months of experiments to arrive at a useful combination of design and technique. Thus, if it had been so simple and possibly straight forward to just use the previously known knowledge from the cooper handcraft including the assembly of longitudinally bent staves with varying widths along their lengths but reinforced by means of barrel straps, this previously known technique would no doubt have been discussed in the publications referred to in the preamble of the present specification.